Anterior epidermis-specific expression of the cuticle gene EDG84A is controlled by many cis-regulatory elements in Drosophila melanogaster

During insect metamorphosis, a pulse of ecdysteroids induces many different morphological changes depending on different parts of the body. In Drosophila, although a number of transcription factors are expressed in a stage-specific manner in response to an ecdysteroid pulse, little is known on the regulatory mechanism for space-specific gene expression during metamorphosis. The EDG84A gene encoding pupal cuticle protein is one of the targets of ecdysteroid-inducible transcription factor βFTZ-F1 and is expressed only in anterior epidermis of the body during mid- to late prepupal period, whereas βFTZ-F1 is expressed in almost all tissues. To address the regulatory mechanism of the tissue-specific expression of the EDG84A gene, we established transgenic fly lines which carry various upstream regions of the gene fused to the LacZ gene and examined the expression pattern of the reporter gene. Results of the transgenic fly reporter assays showed that the space-specific expression is controlled by at least four positive and two negative elements within a 263-bp region near the transcription start site, and at least three of them showed space-specific effects to the anterior body trunk. These results suggest that both high expression level and differential expression are achieved through many cis-regulatory elements.